# -*- coding: UTF-8 -*-
from typing import List
from leetcode_helper import TestcaseHelper, SolutionBase, ListNode, array_to_list, list_to_array


class Solution(SolutionBase):
    # 解题的方法，命名和Leetcode的保持一致即可
    def swapPairs(self, head: ListNode) -> ListNode:
        if not head:
            return None
        if not head.next:
            return head

        node1 = head
        node2 = node1.next
        new_head = node2.next
        node2.next = node1
        node1.next = self.swapPairs(new_head)

        return node2


if __name__ == '__main__':
    solution = Solution()

    # 按照leetcode的题目说明，将基本的test case填入
    # 每条case的最后一个元素是正确的结果，即期待的结果
    # 使用元组来保存输入的数据，期待的结果
    testcases = [
        ([1, 2, 3, 4], [2, 1, 4, 3]),
        ([], []),
        ([1], [1])
    ]

    for case_item in testcases:
        # 获取测试用的case和期待的执行结果
        input1 = case_item[0]
        expect = case_item[len(case_item) - 1]

        exec_result = solution.swapPairs(array_to_list(input1))

        # 判断执行结果，输出提示信息
        check_result = solution.check_result(expect, list_to_array(exec_result))
        TestcaseHelper.print_case(check_result, case_item, list_to_array(exec_result))

